We see a lot of questions that go something like this:
I would like to not only block particular emails but also send them back to the sender so they know they've been rejected. Is that possible. Right now I can only send them to the Junk email folder. Thanks.
Yes, you could do this (using an autoreply rule), but why? If the message is from a spammer with a legitimate address, all you are doing is letting them know your address is valid. If the address is fake, you create more needless traffic and the only result will be the need to delete the NDR you'll get back.
There are a very few circumstances when it makes some sense to reply to unwanted email - but you should do it just once and type a short note asking the sender to stop sending you messages.
- If the address belongs to someone you know but don't want to be in contact with, reply to the sender and ask them to stop sending you email. Or just delete the message and forgot about it. This method works best with former coworkers, family members, etc., that you no longer want to receive email from.
- If it’s from a company and you can't get unsubscribed from their mailing list, reply and ask to be removed then set up a rule to delete the messages and forget about it.
When the sender is a spammer, just delete the message and go on. If you send an autoreply one of two things will happen: you'll get an NDR back or you'll confirm you address is valid and end up with a lot more spam. Since most spammers use fake from addresses, you don't have to worry too much about confirming your address. It is also mostly useless to add spammers to your blocked senders list as their addresses keep changing.
Bottom line: delete the unwanted messages using the junk mail filter and/or using a rule and forget about it.